The invention relates to a crosscut fence for machine tools, in particular panel saws, having a guide bar, on which a first pivotable throwover stop or workstop abutment is mounted in a longitudinally displaceable but fixed manner, and is connected to a measurement and display unit which determines and displays the relative position of the pivotable throwover stop to the guide bar, and in which a rod can be telescopically extended and retracted and which at its free end bears a second pivotable throwover stop.
So that it is possible to manufacture dimensionally accurate workpieces by means of machine tools, the blanks to be machined are positioned by means of so-called stops on the machine, after said stops have been adjusted according to the desired dimensions of the workpiece.
Panel saws are primarily used to cut to size panels, boards and battens from wood or plastic, for example by means of angular cuts, parallel cuts and cuts along the grain. In this case a so-called crosscut fence or left-hand stop is used to adjust the desired material dimensions, which essentially consists of a guide bar mounted on the cross slide and at least one pivotable throwover stop, against which the workpiece abuts during cutting to size.
As is known, mechanical or electronic measurement systems are used to adjust and indicate the distance from a pivotable throwover stop to the cutting tool. An electronic measurement system may consist of, for example, a magnetically coded measuring tape mounted along the guide bar, a sensor which is connected to a pivotable throwover stop and scans the measuring tape without contact and also a switching arrangement processing the readings recorded by the sensor and a display unit optically representing the distance measurement (German Utility Model 91 14 150.8).
The utilisation of several fold-down pivotal throwover stops disposed on a guide bar is also known for different measurement ranges. In this case a first displaceable pivotable throwover stop can be connected to a sensor recording its relative position and a second pivotable throwover stop can be securely connected to a telescopic rod which is mounted in a telescopic and displaceable manner inside the guide bar. With such a stop, to determine the distance of the two pivotable throwover stop with an electronic system, a measuring tape on the telescopic rod and the guide bar and also two sensors are required, as a result of which the manufacturing costs are relatively high (German Utility Model 92 07 797.8).
The object of the invention is to make available a crosscut fence which can be manufactured at a favourable cost, with which the relative positions of several pivotable throwover stop can be simply determined and adjusted in relation to the operation in various measuring ranges by means of a single measurement and display unit and a measuring tape.
The object is achieved by a crosscut fence of the above-mentioned type in that a coupling placed at the measurement and display unit detachably connects the rod with the measurement and display unit. By such a mechanical coupling the relative positions of two pivotable throwover stop can be determined and also adjusted by simple means and in particular independently of one another with only one sensor and a magnetically coded measuring tape.
The coupling advantageously consists of a stop bolt, which can move transversally to the longitudinal axis of the rod and which can be introduced into a bore in the rod, as a result of which a coupling is produced in a simple manner, which, for example, can be manually operated with a knob.
With the engagement of the coupling, the measuring range of the measurement and display unit is advantageously switched over to the second pivotable throwover stop, as a result of which this can be quickly adjusted to the desired distance, in particular with a frequent change-over between the measuring ranges. The change-over may be performed, for example, by an electrical switch on the coupling.
An embodiment in which the connection between the first pivotable throwover stop and the measurement and display unit is detachable is also advantageous, so that, after the first pivotable throwover stop has been fixed in the desired position, the adjustment of the second or a further pivotable throwover stop can be performed by coupling the measurement and display unit, without the first stop, which has already been fixed, having to be moved again.
An advantageous refinement lies in that the rod with the second stop flap can be stopped in relation to the striker bar so that the second pivotable throwover stop can be fixed in the desired position on the guide bar by a clamping device which is easy to operate.
With a pivotable stop, in which a third pivotable throwover stop is guided in a longitudinally displaceable manner on the guide bar and can be stopped in relation thereto and can also be coupled to the measurement and display unit, three distance measurements of the pivotable throwover stop from the tool can be adjusted in different measuring ranges and be activated by folding down the pivotable throwover stops. If the coupling for the third pivotable throwover stop consists of a drag stop which only responds to pressure, with the abutment of which the third pivotable throwover stop has a defined distance from the first pivotable throwover stop the adjustment of the third pivotable throwover stop can be achieved in a particularly simple manner and as a result of the fact that the drag stop is adjustable.
A fast exchange of the measuring range is possible if the pivotable throwover stops can be swivelled in a known manner out of an active position into an inoperative position and their swivelling changes the measuring range of the measurement and display unit, for example by electromagnetic switches, and if, when the drag stop is adjacent, the measuring range of the measurement and display unit is switched over to the third pivotable throwover stop.
The present invention is described below for the sake of example with reference to the attached drawings.